Five cases of pseudotumoral lung formations in workers exposed to nonsilicaceous dusts were described. Four workers, 43 to 58 years old, who were involved in magnesium-hydroxide (1309428) and calcium- hydroxide (1305620) production developed coin shaped lesions, 1 to 2 centimeters (cm) in diameter, on their chest X-rays. They had been exposed to airborne dust concentrations of 0.8 to 128mg/m3 for 17 to 34 years. The lesions were thought to be secondary neoplasms; however, efforts to locate primary tumors were unsuccessful. The patients were monitored annually with chest X-rays. In three patients the lesions demonstrated no change after 5 years. In the fourth, the lesions increased in size by about 30% after 3 years. A thoracotomy which removed a subpleural encapsulated node was performed. The node consisted of inflammatory parenchymal tissue that contained collagen fibers and minute calcified particles. Chemical analysis revealed the presence of calcium-diphosphate (7758238) and magnesium-diphosphate (7757860). Silica (14808607) was not detected. The fifth case was a 45 year old male who worked in a natural rubber processing facility and was exposed to talc (14807966), mica (12001262), and fecula dusts at concentrations of microns long. The patient's chest X-ray revealed an irregular digitated shadow 3.5cm in diameter at the base of the left lung. Other coin shaped lesions appeared in both lung fields 30 to 90 days after the initial examination. The lesion was identified as a giant cell talc granuloma that contained talc fibers and fecula granules. All five subjects were removed from exposure. They have remained in good health with no further lesions developing. The authors conclude that inhaling dolomite (1317653) dust probably caused the coin lesions in the magnesium-hydroxide and calcium-hydroxide production workers. The granulomatosis in the rubber worker was probably due to a reversible flogistic tissue reaction induced by talc.